This week Alex Salmond was gifted the sort of opportunity he is supposed to dream of. A widely disliked silver spoon English Tory chancellor, who even cried at Margaret Thatcher's funeral, chooses England's national day to tell Scots in his iciest manner that the UK may not allow an independent Scotland to form a currency union with sterling. Oh, and the familiar Scottish banknotes might not survive the split either.

As English red rags waved in front of proud Scottish bulls go, George Osborne's Glasgow speech was as provocative as they get. And with David Cameron having made his own trip north this month to celebrate Britain's Trident nuclear weapons – historically unpopular in Scotland – it is hard to imagine two events better calculated to present Salmond with a tailor-made nationalist opportunity.

But Salmond's low-key response was telling. It would be untrue to say that he did nothing in reply. But he hasn't come out swinging, either. Though desperate to get Cameron into a TV debate before the referendum in September next year, Salmond has kept his powder dry. The SNP has been content to leave the detailed responses to senior lieutenants: Nicola Sturgeon and Angus Robertson on the Cameron defence speech; and, this week, John Swinney and Stuart Hosey on Osborne's currency challenge.

This reluctance of Salmond to be drawn into open political combat with the Westminster government is striking. It is a powerful reminder both that Scottish politics is a long game, and that the SNP does not automatically command the field. It says that Salmond does not want to be drawn into the open before a time of his own choosing – closer to the referendum. But it also says that English Tories feel confident enough of their unionist case on Trident and the pound to mount serious counter-arguments in Scotland without fear of the usual humiliation.

Even more significantly it suggests that both sides suspect, surely rightly as things stand, that Scots will vote no when the referendum comes. The consistency of the opinion polls on independence is striking. Support for separation is stuck at around a third of voters. An early poll after Salmond accepted the revised wording of the independence question in January – "Should Scotland be an independent country?" – showed 32% yes, 47% no and 20% undecided. A poll this month for the Daily Record showed a slight swing against independence – 30% yes, 51% no, 19% undecided.

That doesn't make a no vote a done deal. But it makes it the working assumption. Of course, the final numbers will matter in the years beyond 2014, whatever the outcome. A wafer-thin yes vote on a 50%-60% turnout, for instance, might be fragile, especially if Labour campaign in 2015 on a pledge to think again. Likewise, Scottish politics after a no vote will depend on the size of the minority: a 45% yes spinnable as a minor triumph for the SNP, a 30% yes more traumatic. Either way, the SNP could well win the next Holyrood elections in 2016.

September 2014 is still a huge moment, of course. But the default assumption that Scots will vote no has created an important dynamic. Increasingly, Scottish politics is focused beyond, as well as on, 2014. Granted, SNP realists like Salmond are hoping for something to turn up, and will put their shoulders into making it happen. An economic upturn, currently improbable, could be a game-changer. But it bears repeating that Salmond did not really want this referendum. The unexpected SNP landslide in 2011 dumped him with it. His more realistic long-term goal is to win a third SNP term in 2016.

What is really striking about Scottish politics this spring is not the strength of the mood for independence. The striking thing is the sudden buoyancy and, in some cases, seriousness of much of the work that is gradually emerging from the other political parties and from parts of civic Scotland. The most remarkable thing of all is a paradox: the calling of the independence referendum, far from acting as a springboard for a much more confident and assertive nationalism, seems to have become the catalyst for some significant and welcome rethinking about the nature of unionism.

Some of this comes from within the pro-union parties. But the differences in their positions are major. Osborne this week made a case for the status quo, though Scottish Tories are already talking about further devolution. The Lib Dems, in a commission led by Menzies Campbell, want the home rule federalist route. Labour, by contrast, is more concerned with spending. Its Powers for a Purpose document, published a week ago, envisages the eventual full devolution of income tax to the Scottish parliament. Some Labour MPs don't like this, perhaps because they dislike devolution in any shape, or perhaps because they have not grasped that income tax only accounts for 25% of government revenue. But that argument will matter immensely if Ed Miliband becomes prime minister of an unchanged UK.

These issues about new devolved powers and the allocation of taxing and spending are unstoppable now. That is why it is not necessarily correct to say that Salmond will be the ultimate winner even if he loses in 2014. That depends on whether the pro-union forces can coalesce around a robust new devolution settlement within the UK. That hasn't happened yet. But it could.

Both constitutionally and fiscally, the status quo is not on offer, not least because Holyrood will automatically get significant extra tax responsibilities in 2016 if Scots vote no in 2014. But Labour's document is particularly important because it makes a coherent case for UK-wide welfare solidarity – an essential principle in any progressive unionist settlement – and because it resists the unthinking stampede down the route of "devo max", which is independence in all but a formal sense. However, if UK-wide welfare solidarity, why not UK-wide health solidarity too? These issues need much wider thought.

Some of that thinking is already taking place. It is not just Scots who need to get alongside it. English opinion has a much neglected responsibility to get involved too. Edinburgh University Press's new book Scotland's Choices, a hard-headed non-scary guide to the practical options facing Scotland and the UK, is a very good place for active citizens to start. It is a key text, because it reminds us of wider realities. September 2014 may settle one question. But it throws open a dozen more, with implications that stretch across the whole UK.